9
3394.91 kHz. The CW power output while using the CW filter went from 50 watts to
110 watts. I also soldered a short loop of wire to the center lug of the carrier null pot to
serve as a test point to measure the carrier oscillator frequency. Be sure that once you
have determined the filter center-frequency, you place the oscillator frequencies no closer
than about 1.4 kHz and no further than 1.6 kHz from the filter center-frequency.
To recap, we are actually matching the response between USB & LSB by ear, then
verifying with a frequency counter that the carriers are no closer to the filter passband
than 1.4 kHz, and no further than 1.6 kHz. Even though we can match the pitch between
USB and LSB with our ear, we can't tell exactly WHERE they are -- only that they are at
the same point on the filter slope.
When the carrier oscillator frequencies are changed, the signal level of the oscillator
outputs may consequently change and therefore should be adjusted to be equal. Connect
a scope or RF probe to the carrier null pot center lug test point and switch between
sideband modes, checking for equality in level. If need be, adjust the value of R6 or R7
to achieve equality. The level should be at least 1 volt RMS, or 3 volts P-P.
Stabilizing Meter Zero Settings:
S-meter zero setting instability is mainly caused by heat-related resistance changes in the
R106 22KΩ 1-watt resistor on the I.F. board. Replace R106 with a 22KΩ 2-watt
wirewound (Figure 3).
The problem of the meter reading below zero during transmit while in the ALC position
is corrected by connecting a 10MΩ resistor from the meter Zero-Adjust pot pin 3, to pin 2
of T-102 on the I.F. board (hints from N4NRW).
After all the above mentioned changes are made, give the rig a touch up alignment and
enjoy a much improved vintage rig!
Many thanks to Lenny WB8JCJ for his help in editing, image scanning, input, and
implementation of these changes into his HW-101. His help was indispensable.
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